Suppose I have a rogue facing an enemy spell-caster. My rogue drinks a potion of invisibility, stealths behind the caster, and readies an action to attack when the caster casts a spell. The caster obligingly casts a spell without casting defensively, as he doesn't know the rogue is present, which would normally draw an attack of opportunity. My rogue attacks and interrupts the spell, but does he attack once or twice?

Can a character get a readied action and an attack of opportunity that is triggered by the same action?

2 Answers
2

A readied action is just a continuation of the player's turn that has been delayed until the occurrence of a certain trigger. Once the trigger requirements have been met (eg. Goblin comes within range of your Fighter,) as long as it is prior to the PCs next turn, the action will be completed.

Now, if an enemy moves through your Rogue's threatened range, or in this case has a Mage cast without defense, as long as the trigger were specified the Rogue would get both his turn's action (the readied action) and the attack of opportunity (with Sneak Attack die only on the readied action, so not a bad ploy at all for some decent damage).

The easiest way to think of it is as the readied action just being a continuation of the player's turn while treating the attack of opportunity like you would in any other situation.

Good damage opportunity + make them lose a spell and an action + getting behind the casters and away from the tanks = win!
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C. Ross♦Jun 9 '11 at 13:38

2

Do remember, the rogue will only get sneak attack dice for the first attack since after that they are no longer invisible. Beyond that, I'd consider this the perfect answer.
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Matrix MoleJun 9 '11 at 15:27

1

Nice answer! It is good to note though, that if the caster is smart and sees you vanish, they'll either five foot in a direction next time they cast to try and get away (still good chance of eating an attack from you), and cast defensively anyhow. Fortunately, I've not yet seen a caster who's remembered to do that! :D
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CthosJun 9 '11 at 15:30

@Matrix Mole - I thought I had implied that in my post but realized I had done so in a quasi-ambiguous manner. Post edited to reflect that.
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GPierceJun 9 '11 at 17:41

Seems a bit unfair to the victim. Take the readied action, and if the spell is ruined the ao condition no longer exists, and vice-versa. If the spell is not ruined, then the ao or readied condition is satisfied again so you can swing again. You can't take two standard actions simultaneously, so your ao and readied conditions need to be for two separate events if you want to be guaranteed to get both actions. I'm considering 'starting to cast'and 'continuing to cast after being attacked' as separate events, although I admit that's debateable.